The present invention relates to friction elements such as clutch facings and the method of making such elements utilizing woven glass fiber rovings as the reinforcing and friction material.
Conventional clutch facings for automotive service employ asbestos yarn and a non-ferrous wire like copper, brass, or zinc which are twisted together, treated with a friction cement, wound into preforms, molded and finished. As spin strength requirements for clutch facings became more demanding, glass fibers were used to strengthen the facings while retaining asbestos fibers for the friction material. However, it was not until the inventions disclosed in application Ser. No. 156,267 filed June 24, 1971, now U.S. Pat. No. 3,756,910 and Ser. No. 156,410 filed June 24, 1971, now U.S. Pat. No. 3,743,069 that glass fibers were used with non-ferrous metal and cement to provide a friction element with glass fibers as both the reinforcing and friction material.
It is an object of the present invention to provide an improved friction element which has excellent spin strength and frictional properties. It is a further object of the present invention to provide a method of producing such a friction element from woven glass fiber rovings which is faster and more economical than previous methods employed.
The improved friction element is achieved by providing a disc having continuous, untwisted parallel strands of glass fiber extending in a circumferential direction in the disc to provide the required spin strength. The friction element also has strands of glass fiber extending in a direction that is generally normal to the face of the disc to provide excellent frictional properties. The disc is either provided with non-ferrous metal chips which are dispersed throughout the disc or non-ferrous metal wires which are included in the circumferentially and/or normally extending strands of the disc.
The improved method of forming the friction element comprises forming a glass fabric of continuous parallel glass warp strands and continuous parallel glass fill strands; passing the fabric through a bath of heat curable cement to impregnate the fabric; winding the fabric onto a mandrel to form a spirally wrapped cylinder; slicing the cylinder into disc preforms; and molding said disc preforms under heat and pressure. Non-ferrous metal is incorporated into the friction element by either depositing non-ferrous metal chips on the fabric prior to wrapping the fabric on the mandrel or including non-ferrous metal wires in the warp and/or fill strands.